Apparatus and process for storage of dry ice



Jan. 6, 1942.

W. T. BIRDSALL APPARATUS AND PROCESS FOR STORAGE OF DRY ICE Filed Nov.4, 1937 2 Sheets-Sheet 2 Patentecl Jan. 6, 1942 APPARATUS AND rnoonssFon" STORAG e OF DRY ICE Wilired T. Birdsall, deceased, late ofMontclair,

N. J., by Alvin C. Birdsall, administrator, Washington, D. C., assignorto Mergenthaler Linotype Company, Brooklyn, N. Y., a corporation of NewYork Application November i, 1937, Serial No. 17:2,715

` 5 c'aimsl (c. (az-91.5 e l i 4 This invention relates to thepreservation of materials which tend to melt, evaporate or sublime,under conditions of ordinary atmospheric pressure and temperature andparticularly to the preservation of low temperature refrigerants such asdry ice and liquid air.

to or from the stored material is .reducedor eliminated. a

The desired result is attained bydoing two things; first, by reducingthe flow of heat as much as possible, and second, by dive'rting'theremaining heat in a manner to prevent continued change in equilibriumconditions.

The flow of heat to the stored material may be reduced by surroundingthe storage space with material of low heat conductivity such as balsaWood, kapoc fibre, cork board, orother heat insulating materials .suchas those described in applicant's co-pending application' Serial No.172314 filed Nov. 4, 1937, andalso may be reduced by the use of furtherelementsof design, Construction or material which make such" insulationmore efiective for its purpose. e such an element would'be an additionallayer. of material of high heat conductivity such, as copper or aluminumdisposed upon either or both surfaces of the material of lowthermal'conductivity in a manner to prevent localized differences intemperature which might result in the flow of considerable heat througha small area of .the

insulation, or the creation of temperature dif ferences inside thestorage space withthe formation of `destructive convection currentsaround the stored material. A similarly functioning element would be acoil of pipe forming the desired isothermal surface and filled with amixture of a suitable volatile fluid and its vapor whereby condensationof the vapor in the pipe automatically will heat any portion thereofwhich becomes too cold, while evaporation of fluid will cool any pointwhich becomes too warm.

In order to 'divert any heat penetratng .the

the invention. v I

the stored material, means are employed; which are hereinafter referredto as a "guafd ring, and which serve to absorb or remove from theinterier of the casing such heat as may pe'netrate the insulation. Thisguard ring insome instances may consist of the outermo st' layers of acharge of the stored material itself but preferably consists of materialseparated from 'that being stored and interposed between thestoredmaterial and insulation;

In most cases the material used in the guard ring is one which absorbsheat by 'a change of state. However, a fluid may be used' which absorbsthe undesired heat by a Chemical or physical change other than a changeof state. For instance, :benzoL 'certain mineral oil' distillates, andmany other materials when passed over the surface of solid dry icedissolve some of the ice and thereby reduce its surface temperature. Thematerial which produces -this result can be reactivated (with theevolutiofrof 'the dissolved refrigerant in vapor form) by slight warmingso that it can be circulated continuously. ObViously othermethods andmeans for absorbing heat may be used in 'the guard ring of -the presentinvention.

In order to illustrate the invention more fully, reference is madehereafter to the accompanying figures of the drawings, each of .which isa diagrammatc representation of an alternative form of means adapted foruse in the practice of In the drawings: i r

Figures 1 and 2 represent one typical installation for the storageof dryice;

tFigure 3 represents mechanism particularly designed for thepreservationof materials such as liquid air and the like; and

`Figures 4, 5 and 6 illustrate mechanism which is particularly useful invarying the operation of the guard ring.

Inthat form of the invention villustrated in Figure 1 the guard ringembodies a chamber 2 formed of insulating material such as cork board,kapoc, cellular insulation or the like within which islocated a metallicliner 4of copper, aluminum or other material which is a good heat'conductor. The chamber 2:'is preferably located 'in a depression 6 inthe earth 'so that a layer of cold air will accumulate above thesurfa'ceof the chamber so as to shield the upper portion thereof from heattransfer to the stored' material from above.

The material 8 to be stored 'is'represented as insulation and thusfurther aid in preserving blocks of dry ice or the like immersed ina'highly viscous liquid or any other continuous or substantiallycontinuous medium o serving to prevent or reduce diffusion of vapor fromthe stored material and further diminish the flow of heat to thematerial by avoidance of convection currents in the space about thestored material. Since most liquids or substances employed as the mediumin contact with the dry ice are very viscous or stiff, such substancesare referred to in the claims as a substantially fluid" medium.

In this Construction heat which tends to flow toward the material fromexternal sources through the walls of the chamber 2 or otherwise isdistributed about the material due to the heat conducting liner 4 sothat but very little heat flows inwardly through ea'ch separate unit ofsurface of the liner. The blocks of stored material l I, which arelocated adjacent the walls of the chamber, receive any heat whichpenetrates the liner and which is transmitted thereto through the mediumID surrounding the stored material.

Due to the presence of the medium ID in and about the stored material,heat can be transferred to the stored material only by conduction, sinceconvection and radiation are substantially eliminated. For this reasonheat flowing inwardly toward the stored material reaches only thoseblocks 'of material H which are closest to the liner 4, whereupon it isabsorbed as latent heat of vaporization at the surface of the outerblocks within the chamber. Heat does not penetrate to the inner blocksor even beyond the outer surface of the outer blocks within the chamberso that destruction of the stored material and disturbance ofequilibrium conditions within the main body of stored material isreduced to a minimum. Thus the outer surface of the blocks H of thestored-material constitutes the guard ring protecting the inner storedmaterial.

If broken or scrap dry ice is located about the blocks 8 heatpenetrating the insulated walls of the chamber does not destroy theblocks or disturb the condition of thermodynamic equilibrium between thesolid and vapor of the material in storage and only the scrap materialis destroyed. As illustrated in Figure 2, the stored material 8 islocated within an inner casing l2 and is immersed in a highly viscousliquid or other medium O serving to prevent the creation of convectioncurrents about the stored material; The broken dry ice l4 or other meansemployed for preventing or compensating for heat transfer to the storedmaterial f or convenience is located between the casing l2 and thechamber 2 so as to be separated from the stored material. Means such asthe coil IS 'containing a Volatile refrigerant may be used as aniso-thermal device to prevent localized heat transfer to the storedmaterial. The coil may also serve to aid in absorbing heat flowinginwardly through the Chamber 2 and may be used either by itself or in conjunction with the broken dry ice l4 to absorb heat flowing into or outof the stored material. A suitable cover such as the dry ice containingreceptacles !8 may 'be located on the top of the casing !2 to furtherprotect the stored material from the influence of external heat and asubstantially non-fluid medium 2!! such as a highly viscous liquid orcomninuted or fibrous material serving to prevent the creation ofconvection currents may surround the broken dry ice.

By constructing the inner casing |2 of heat insulating material orapplying heat insulation to the casing, it is possible further to guardthe stored material from the influence of external heat since that heatpenetrating the outer chamber 2 is taken up by the broken dry ice orother heat absorbing means between the chamber and the casing !2.Furthermore, a temperature differential is preserved between the heatabsorbing means and the stored dry ice due to the insulating characterof the casing [2. In this Way equilibrium is maintained and the materialpreserved without material loss or evaporation thereof, and the rate ofevaporation of the broken dry ice is limited to that necessary toprotect the stored material from external influences.

In those cases wherein the material being stored is in theform of blocksstacked in tiers and surrounded by a liquid or plastic substanca, thoseblocks in the lower tiers are subjected to greater hydrostatic pressurethan those blocks in the upper tiers. Those blocks in the upper tierstherefore tend to sublime or evaporate more rapidly and at lowertemperatures than those in the lower tiers so that it may be desirableor necessary to provide more effective heat absorbing means about theupper portion of the storage casing than about the lower portionthereof. In some instances, the guard ring may in fact. be located aboutonly the upper portion of the casing, particularly when the material 20surrounding the broken dry ice is relatively fluid and serves to flowdownwardly about the exterior of the casing.

As illustrated in Figure 3 of the drawings, the material to be stored,which may be liquid air, is of a homogeneous character' and is locatedwithin a receptacle 22 spaced from an outer chamber 24 surrounded byinsulation material 26. Additional liquid air or other heat absorbingmeans 28 is located between the receptacle 22 and chamber 24 to absorbheat passing inwardly toward the stored materiaL The function andoperation of this form of device is substantially the same as that ofFigures 1 and 2 and is especially applicable for the storage of liquidrefrigerants. Evaporation of the liquid air or heat absorbing means* inthe space between receptacle 22 and chamber 24 prevents the transfer ofheat to the stored material while the temperature of theliquid airitself remains` the same and is sufiiciently low to preserve that withinthe receptacle. A

In the Construction of Figura, 4.. the g-uard ring is provided withbroken dry ice 30 or other material having a high latent heat ofvaporization and a solvent 32 for the vapor of the dry ice or othermeans for removing said vapor. is placed in contact or communicationtherewith; Circulation of the solvent in contact with. the dry icecauses the latter to evaporate at a rate which may be controlled at willby the introduction of fresh solvent to vary the amount of heat taken upby the guard ring. Recirculation of the solvent may be effected bydrawing off the same after it has become partially or completelysaturated so as to permit evaporation of the dissolved vapor, and returnthereof to the system in a regenerated state. As shown, an outlet pipe34 is provided for conducting saturated solvent to an evaporator 36'from which' it is returned as desired through a pipe 38.

With this Construction the material evaporated in the guard ring mayhave a higher or lower vapor pressure than the material to be preservedand the temperature of the guard ring may be reduced below that of thestored material. Very effective protection of the material from theinfiuence of external heat is thus provided and any heatproduced bycondensation of vapor of the stored material due to an increase inatmospheric pressure or other changing conditions is readily absorbed.

In a similar manner evaporation of the material in th guard ring toabsorb heat tending to flow into or out of the stored material may beefiected by the construction illustrated in Figure wherein the guardring isclosed at the top and a pump 40 is provided to draw off vapors ofthe material 42 therein. Pressures below or above that of the atmospherecan be applied to the material in the guard ring so that the rate ofevaporation and amount of heat absorbed by the material in the guardring may be carefully and Conveniently controlled to insure storage ofmaterial in chamber 44 without transfer of heat thereto fromexternalsources. The same means can be employed to compensate for otherforms of energy transfer to the stored material, such as changes inatmospheric pressure, which tend to disturb equilibrum conditions in thestorage material.

In the Construction of Figure 6 the rate of evaporation of material inthe guard ring is controlled by varying the hydrostatic pressure towhich the evaporating material is subjected. For this purpose thechamber 48 in which material 50 is stored is provided With heatinsulating means 52 spaced therefrom to provide a guard ring withinwhich broken dry ice 54 or other material to be evaporated is located. Amedium 56, such as a 1iquid,-surrounds the broken dry ice and extends toa level which may be considerably above the broken dry ice. Change inlevel of the liquid is eflected by supplying additional liquid to thespace about the chamber or withdrawing liquid therefrom through -thepipe 58 connected to a liquid reservoir 60. The reservoir is closed atthe top and provided with a two-way valve 62 for supplying compressedair to the reservoir to force liquid therefrom to raise the level ofliquid above the broken dry ice so as to increase the hydrostaticpressure and reduce evaporation thereof when the amount of heat flownginwardly through the heat insulating means is low. Upon increase in theheat so transmitted, or other energy change giving rise to heat withinthe storage chamber, the valve 62 is operated to release the pressure onthe liquid in the reservoir and allow the liquid in the guard ring to belowered by drainage through pipe'58 to the reservoir 60. The hydrostaticpressure is thus reduced, permitting more rapid evaporation of th brokendry ice so that a prevent or compensate for transfer of energy to i orfrom the stored material. However, it should b'e understood that theconstructions shown and described are intended to be illustrative of theinvention rather than to limit the scope thereof.

What is claimed is:

1. A method for the preservation of low temperature refrig erants suchas dry ice, liquid air and the like, which comprises the steps'ofenclosing the refrigerant in an insulated chamber, surrounding thechamber with a barrier of dry ice immersed in a liquid and insulatingsaid dry ice from its surroundings.

2. A method for the preservation of low temperature refrigerants such asdry ice, liquid air and the like, which comprises the steps ofsurrounding the material to be preserved with a similar low temperaturerefrigerant immersed in a liquid and controlling the rate at which thesurrounding low temperature refrigerant evaporates by varying the levelof said liquid.

3. A structure for use in the storage of low temperature refrigerantscomprising an insulated chamber for receiving material to be stored,heat insulating means spaced from the walls of said chamber, and a heatabsorbing barrier comprising dry' ice immersed in a liquid located inthe space betwen said chamber and said heat insulating means' 4.Apparatus for storing dry ice comprising a storage chamber enclosing thedry ice to be stored, a heat insulating casing surrounding and spacedfrom said storage chamber, additional dry ice in the space between saidheat insulating casing and said storage chamber and means movable intoand out of contact with said additional dry ice to vary the rate atwhich heat is absorbed thereby.

5. Apparatus for storing dry ice comprising a storage chamber formed ofinsulating material, a casing formed of insulating material spaced fromsaid storage chamber and surrounding the same, dry ice 'located in thespace between said storage chamber and casing, removable cover membersfor the storage chamber each containing additional dry ice andsubstantially fluid media surrounding the dry ice in said storagechamber and the dry ice in said cover members and in the space betweensaid casing and storage chamber. i

- ALVIN C. BIRDSALL, Administrator of the Estate of W'lffed T. Birdsall,Deceased.

